JPH06283866A - Multilayer circuit board and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide a multilayer circuit board formed substantially of a copper foil and a polyimide resin layer and having excellent chemical resistance, curling resistance and adhesive and a method for manufacturing the same, and to obtain the board adapted for connection reliability and high density mounting by facilitating its connection. CONSTITUTION:One-side boards in each of which a copper circuit 1' is formed on one side surface of a low linear expansion polyimide resin layer 2 and the other surface is etched or charged are adhered and laminated through thermoplastic polyimide resin layers 3 in a multilayer structure. Through holes are provided at the layer 2, a conductive passage in which metal 4 is filled is formed, and further bumped metal protrusions 5 are formed to enhance electric connection reliability.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer circuit board and a method for manufacturing the same.

[0002]

2. Description of the Related Art In recent years, as electronic devices have become lighter, thinner, and smaller, it is necessary to make circuit boards thinner and more dense. In general, as a circuit board, a copper foil and a polyimide resin layer are laminated with or without an adhesive.
Although a layer type or a two layer type substrate is used, many two layer type substrates which are not affected by the characteristics of the adhesive have been proposed. Further, there is an increasing demand for development from a single-layer substrate to a multi-layer substrate for higher density and higher performance, and various structures and manufacturing methods have been proposed in response to this.

As a method for obtaining such a multilayer circuit board, for example, a method in which a thermoplastic polyimide resin layer is used as an insulating substrate and thermocompression bonding is applied to form a multilayer structure, the thermoplastic polyimide resin used in this method is used. Is inferior in heat resistance, chemical resistance, and dimensional stability to a thermosetting polyimide resin that is usually used for an insulating substrate, and thus has a practical problem. Further, the thermoplastic polyimide resin generally has a linear expansion coefficient of about 2 to about the linear expansion coefficient of the copper foil.
There are four times as many, and there is a risk that the substrate will curl when the wiring circuit is patterned on the copper foil.

On the other hand, even if a thermosetting polyimide resin layer is used in place of the thermoplastic polyimide resin layer used in the above method, since the thermosetting polyimide resin layer itself does not have an adhesive function, it is difficult to stack it in a multilayer structure. Also, cracks may occur due to mechanical brittleness. Further, although the low linear expansion polyimide resin layer satisfies practical properties (strength), it generally has a drawback that the adhesive force to an adherend is poor.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, in which a copper circuit pattern is formed on an insulating resin layer substantially made of a polyimide resin layer and laminated in multiple layers. It is an object of the present invention to provide a multilayer circuit board having excellent chemical resistance, curl resistance, and adhesiveness, and a method for manufacturing the same.

[0006]

The inventors of the present invention have conducted extensive studies to achieve the above object, and as a result, a specific surface treatment is applied to one surface of the low linear expansion polyimide resin layer,
It was found that a multilayer circuit board achieving the above object can be obtained by stacking a plurality of circuit boards having a circuit pattern formed on the other surface by utilizing the adhesive function of a thermoplastic polyimide resin, and completes the present invention. Came to. Further, it has been found that the use of a polyimide precursor has extremely excellent adhesiveness in the production of such a multilayer circuit board.

That is, according to the present invention, a circuit board having a low linear expansion polyimide resin layer on one side of which an etching treatment or a charging treatment is performed and on the other side of which a circuit is laminated is formed with a plurality of circuit boards through a thermoplastic polyimide resin layer. A multilayer circuit board formed by stacking, in particular, at least one through hole is formed in the thickness direction in the low linear expansion polyimide resin layer and the thermoplastic polyimide resin layer in or near the circuit formation region, A through-hole formed in the formation region is provided with a conductive path and a bump-shaped metal protrusion made of a metal substance, and the circuit board is provided with electrical continuity via the bump-shaped metal protrusion, In addition, a step of coating and drying a low linear expansion polyimide precursor solution on a copper foil, a step of subjecting the coated surface to an etching treatment or a charging treatment, and 400 in an inert gas atmosphere. A step of imidizing the precursor layer by heating at the above temperature, a step of forming a circuit by patterning a copper foil to obtain a circuit board, and a plurality of circuit boards through a thermoplastic polyimide resin layer. The present invention provides a method for manufacturing a multi-layer circuit board, which comprises a step of thermocompression bonding.

The insulating resin layer used in the multilayer circuit board of the present invention is substantially composed of a polyimide resin layer. Such an insulating resin layer has a laminated structure of a low linear expansion polyimide resin layer and a thermoplastic polyimide resin layer, and has a copper circuit formed on the other surface of the low linear expansion polyimide resin layer. A plurality of single-layer circuit boards are laminated to form a multilayer structure. The low linear expansion polyimide resin used in the present invention has a linear expansion coefficient of 2.0 × 10 ⁻⁵ cm / cm / ° C. or less, and the thermoplastic polyimide resin has a glass transition temperature of 200 ° C. As described above, the melt viscosity at 390 ° C. is defined as having a property of 10 ⁹ poise or less. In order to improve the coating workability and the adhesiveness between the resin layers, these polyimide resins are preferably subjected to a coating step as a polyimide precursor solution, and then subjected to heating, dehydration ring closure, and imidization.

The low linear expansion polyimide resin and the thermoplastic polyimide resin are not particularly limited as long as they meet the above definitions, but the low linear expansion polyimide resin is 3,3 ', 4 as a tetracarboxylic acid component. , 4'-
Biphenyltetracarboxylic dianhydride, pyromellitic dianhydride, bis (3,4-dicarboxyphenyl) sulfone dianhydride, 2,2 ′, 3,3′-biphenyltetracarboxylic dianhydride, 3, At least one of 3 ′, 4,4′-benzophenone tetracarboxylic dianhydride is used, and p-phenylenediamine is used as the diamine component.
4,4'-diaminodiphenyl ether, m-phenylenediamine, 3,4'-diaminodiphenyl ether,
It is preferable to use a polymerized product of at least one of 3,3′-diaminodiphenyl ether and 4,4′-diaminobiphenyl.

On the other hand, as the thermoplastic polyimide resin, bis (3,4-dicarboxyphenyl) ether dianhydride, bis (3,4-dicarboxyphenyl) sulfone dianhydride and bis (3,3) are used as tetracarboxylic acid components. 4-dicarboxyphenyl) hexafluoropropane dianhydride,
3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride, 2,2-bis (3,4-dicarboxyphenyl) propane dianhydride, bis (3,4-dicarboxyphenyl) difluoromethane dianhydride At least one of the anhydrides is used, and bis [4- (3-aminophenoxy) phenyl] sulfone, bis [4- (4-aminophenoxy) phenyl] sulfone, bis [4- (4-
Aminophenoxy) phenyl] hexafluoropropane, 3,3′-diaminodiphenyl sulfone, 3,4 ′
-Diaminodiphenyl sulfone, 4,4'-diaminodiphenyl sulfone, bis [4- (3-aminophenoxy) phenyl] ether, bis [4- (4-aminophenoxy) phenyl] ether, bis [4- (3-amino Phenoxy) phenyl] propane, bis [4- (4-aminophenoxy) phenyl] propane, 3,3′-diaminodiphenylpropane, 3,3′-diaminobenzophenone used for polymerization reaction Is preferred. Polymerization is carried out by using N-methyl-2-pyrrolidone, N, N-dimethylacetamide, N, N-dimethylformamide or the like as an organic solvent and mixing the above components in approximately equimolar amounts.

In the present invention, the low linear expansion polyimide precursor obtained as described above is applied onto a copper foil using a roll coater, a comma coater, a knife coater, a doctor blade, etc. and dried to obtain a copper foil / low wire. A single-sided substrate having the structure of the expandable polyimide precursor layer is obtained. In addition, the drying step at this time is performed at a temperature of about 60 to 180 ° C.,
It is preferable that only removal of the solvent is performed so that dehydration ring closure and imidization of the polyimide precursor do not proceed.

Next, the single-sided substrate having the structure of the copper foil / low linear expansion polyimide precursor layer thus obtained is heated to a temperature of 400 ° C. or higher in an inert gas atmosphere to obtain a polyimide precursor. The body layer is dehydrated, closed, and imidized. For heating, a device such as a hot air circulation type heating furnace or a far infrared heating furnace is used. When the heating temperature is 400 ° C. or lower, imidization does not proceed sufficiently and the characteristics peculiar to polyimide cannot be sufficiently exhibited. Further, if oxygen is present during imidization, not only the copper foil surface is oxidized but also the thermoplastic polyimide resin may be thermally decomposed, which is not preferable. Usually, the oxygen concentration is 4% or less, preferably 2%.

After the imidization treatment as described above, the obtained copper foil / single-sided copper foil having a structure of a low linear expansion polyimide resin layer is formed into a circuit in a desired pattern. A well-known method is used for forming the circuit, for example, a method in which a photoresist is coated on a copper foil and the circuit pattern is exposed, developed, and wet-etched.

In the present invention, one surface of the low linear expansion polyimide resin layer (the surface opposite to the circuit forming surface) is subjected to a surface such as an etching treatment or a charging treatment for the purpose of improving the adhesiveness with the thermoplastic polyimide resin layer. Processing is performed. Specific examples of the etching treatment include wet etching with an alkaline solution and dry etching such as sputter etching, and examples of the charging treatment include plasma discharge treatment. Incidentally, the step of applying such a surface treatment is not particularly limited as long as it is before multilayering via a thermoplastic polyimide resin layer described later, after the formation of the low linear expansion polyimide precursor layer, or by heating it. After the formation, the circuit pattern may be formed either.

A plurality of single-layer circuit boards obtained in this manner are superposed with a thermoplastic polyimide resin layer interposed therebetween,
Using a laminate roll or a hot press, a pressure of 1 to 500 kg / cm ² is applied at a temperature about 30 to 150 ° C. higher than the glass transition temperature of the thermoplastic polyimide resin, and thermocompression bonding is performed to obtain the multilayer circuit board of the present invention. obtain. At the time of this thermocompression bonding, the thermoplastic polyimide resin layer is laminated so as to be adjacent to the low linear expansion polyimide resin layer of the other circuit board to be laminated, but the copper foil is etched in the previous step. Since the surface of the low linear expansion polyimide resin layer is also roughened when forming the circuit, the adhesive strength with the thermoplastic resin is further improved. In this step, in order to prevent oxidative deterioration of the copper foil and the polyimide resin layer, it is preferable to carry out pressure bonding under an inert atmosphere or in a vacuum.
The oxygen concentration is adjusted to 4% or less, especially 2% or less.

In the finally obtained multilayer circuit board, the coefficient of linear expansion of the thermoplastic polyimide resin layer is a ₁ ,
When the total thickness of the thermoplastic polyimide resin layer is t ₁ , the linear expansion coefficient of the low linear expansion polyimide resin layer is a ₂ , and the total thickness of the low linear expansion polyimide resin layer is t ₂ , then a ₁ [t ₁ / (T ₁ + t ₂ )] + a ₂ · [t ₂ / (t ₁ + t ₂ )] and the coefficient of linear expansion of copper is 1.0 × 10 ⁻⁵ cm /
By setting the value smaller than cm / ° C., it is possible to further prevent the deviation of the circuit pattern due to thermal contraction or the like and the curl after etching the copper foil, which is preferable.

The multilayer circuit board of the present invention and the method for manufacturing the same will be described below with reference to the drawings.

FIG. 1 is a sectional view of each step for explaining a method for obtaining a multilayer circuit board of the present invention.

In the present invention, first, as shown in FIG. 1A, a low linear expansion polyimide precursor solution is applied on a copper foil 1 and dried to form a low linear expansion polyimide precursor layer 2 '. To do. After that, this is heated at a high temperature to be imidized, and as shown in FIG. 1B, the copper foil 1 is formed into a desired shape to form a circuit 1 ′. Then, the surface of the low linear expansion polyimide resin layer 2 opposite to the surface on which the circuit 1'is formed is treated,
A plurality of single-layer circuit boards formed as shown in (b) are stacked via the thermoplastic polyimide resin layer 3 and thermocompression bonded to obtain the multilayer circuit board of the present invention shown in FIG. 1 (c). .

FIG. 2 is a sectional view of each step of another manufacturing method for explaining the method for obtaining the multilayer substrate of the present invention. Figure 2
1A is the same as FIG. 1A above, and then FIG.
After forming the circuit 1'as shown in (b), the circuit 1 '
At least one through hole is formed in the low linear expansion polyimide resin layer 2 in the formation area, a conduction path is formed by the metal 4 in this through hole, and bump-shaped metal protrusions are formed on the surface opposite to the surface on which the circuit 1'is formed. Object 5 is formed. The surface of the single-layer circuit board formed in this way is surface-treated in the same manner as in FIG. 1, and then a plurality of layers are superposed with the thermoplastic polyimide resin layer 3 interposed therebetween.
By thermocompression bonding, the multilayer circuit board of the present invention shown in FIG. 2 (c) is obtained.

As shown in FIG. 2, metal 4 is provided with through holes.
It is preferable that the conductive path is formed by a method such as electrolytic plating, and the bump-shaped metal protrusions 5 are further formed, so that electrical connection and conduction can be easily performed when laminated in a multilayer structure. The diameter of the through hole to be formed can be set at any time depending on the application of the substrate, but is usually 1 to 20.
A size of about 0 μm is preferable. Examples of the method for forming the through hole include a wet etching method using an alkaline solution or the like, a dry etching method of irradiating laser or plasma, or a mechanical perforating method, but in particular,
From the viewpoints of processing accuracy, processing speed, manufacturing cost, etc., it is preferable to use a low linear expansion photosensitive polyimide resin and perform photolithography using ultraviolet light having a wavelength of 450 nm or less. However, the perforating process at this time is generally performed in the state of an amic acid, and after making a hole, it is imidized by heating.

The metal species to be filled is not particularly limited as long as it can conduct electricity. For example, metals such as gold, silver, copper, nickel, tin, solder, chromium, tungsten, rhodium, indium, etc., or alloys of these or two are used. It is possible to stack and use one or more species. The bump-shaped metal protrusion 5 is
For example, electrolytic plating is further grown to a height of about 1 to 200 μm.

The method for producing a multilayer circuit board of the present invention is not limited to the above-mentioned method. For example, a low linear expansion polyimide precursor solution is applied on a mirror-finished metal sheet and dried, and then a low linear expansion is applied from the mirror-finished metal sheet. Of the flexible polyimide precursor layer, heating it to imidize it, and then applying a surface treatment to the low linear expansion polyimide resin layer that was formed, and then depositing a metal conductor by vapor deposition, ion plating, sputtering, etc. A single-sided substrate can also be obtained by attaching.
As described above, the single-sided substrate may be laminated with the thermoplastic polyimide resin layer interposed therebetween in order to form a multilayer structure.

FIG. 3 is a sectional view showing another example of the multilayer circuit board of the present invention shown in FIG. 2 (c). In FIG. 3, a through hole is provided not only in the circuit 1'formation region but also in the vicinity thereof, and a conductive path made of metal is not formed in the through hole in the vicinity. When the through-holes thus formed are laminated in a multi-layer structure, the thermoplastic polyimide resin layer 3 is melted and fluidized and filled in the holes, and the anchor effect is exerted to contribute to the improvement of the adhesive strength.

FIG. 4 is a sectional view showing a state in which the semiconductor element 6 is connected to the multilayer circuit board shown in FIG. 3 via bump electrodes.

FIG. 5 shows a state in which the semiconductor element 6 is mounted on the multilayer circuit board of the present invention, bonded by the wire 9, and then connected to the external circuit 7 on the external substrate 8 by the bump-shaped metal protrusion 5. It is sectional drawing shown. The bump-shaped metal protrusion 5 according to the present invention does not need to be formed one by one for each through hole as shown in FIGS. 2 to 4, but as shown in FIG. It can also be formed.

[0027]

EXAMPLES The present invention will be specifically described below with reference to examples.

Example 1 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride and p-phenylenediamine, approximately equimolar, were polymerized in N-methyl-2-pyrrolidone to have a low linear expansion coefficient. Of a water-soluble polyimide precursor solution is uniformly cast on a rolled copper foil (thickness 18 μm) using a comma coater, and the temperature is 100 ° C.
And dried to prepare a single-sided substrate.

The single-sided substrate thus produced was heated at 450 ° C. in a continuous heating furnace having an oxygen concentration of 1.5% or less by nitrogen gas substitution to perform dehydration ring closure and imidization treatment. The thickness of the obtained low linear expansion polyimide resin layer was 30 μm.

Next, the obtained low linear expansion polyimide resin
O on the surface of the layer (the surface opposite to the copper foil surface) ₂Irradiate plasma
(Irradiation conditions: 300 W, 6.5 Pa, 10 minutes)
Surface treatment was applied.

When the copper foil on the one-sided substrate was removed by etching and thermomechanical analysis was performed, the linear expansion coefficient of the low linear expansion polyimide resin layer was 1.0 × 10 ⁻⁵ cm / cm / ° C.
The coefficient of linear expansion of copper was 1.6 × 10 ⁻⁵ cm / cm / ° C.

On the other hand, bis (3,4-dicarboxyphenyl) ether dianhydride and bis [4- (4-
Aminophenoxy) phenyl] sulfone approximately equimolar,
A thermoplastic polyimide precursor solution obtained by polymerization in N-methyl-2-pyrrolidone was cast and applied by the same method as above, and dried at 100 ° C. to form a thermoplastic polyimide precursor film. The formed thermoplastic polyimide precursor film is peeled from the glass plate and heated at 200 ° C. for 1 hour for imidization to form a thermoplastic polyimide resin film (10
μm thickness and coefficient of linear expansion of 5.8 × 10 ⁻⁵ cm / cm / ° C.).

Then, the copper foil on the one-sided substrate is etched to form a copper circuit, and then a thermoplastic polyimide resin film is laminated between the substrates by a vacuum hot press, and the temperature is 350 ° C. and 100 kg / cm. The multilayer circuit board (three-layer structure) of the present invention was obtained by thermocompression bonding under the conditions of ² .

The peeling strength of the multilayer circuit board obtained as described above was 1.5 kg / cm, and peeling occurred at the interface with the copper foil and not between the polyimide resin layers. Further, no void was generated even in the solder dip test at 400 ° C. for 30 seconds, and there was no problem in heat resistance.

Example 2 Approximately equimolar amounts of 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride and p-phenylenediamine / 4,4'-diaminodiphenyl ether (60:40 molar ratio) were used. Polymerization in N-methyl-2-pyrrolidone gives a low linear expansion polyimide precursor solution, which is rolled copper foil (thickness 3
5 μm) was uniformly cast and coated on it by a comma coater, and dried at 100 ° C. to prepare a single-sided substrate.

The one-sided substrate thus prepared was heated at 420 ° C. in a continuous heating furnace having an oxygen concentration of 1.0% or less by nitrogen gas substitution to perform dehydration ring closure and imidization treatment. The thickness of the obtained low linear expansion polyimide resin layer was 20 μm.

Next, the obtained low linear expansion polyimide resin
N on the surface of the layer (the surface opposite to the copper foil surface) ₂Irradiate plasma
(Irradiation conditions: 300 W, 6.5 Pa, 10 minutes)
Surface treatment was applied.

When the copper foil on the single-sided substrate was removed by etching and thermomechanical analysis was performed, the linear expansion coefficient of the low linear expansion polyimide resin layer was 1.7 × 10 ^-5 cm / cm / ° C.,
The coefficient of linear expansion of copper was 1.6 × 10 ⁻⁵ cm / cm / ° C.

On the other hand, approximately equimolar amounts of bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride and bis [4- (3-aminophenoxy) phenyl] sulfone were mixed on a glass plate with N-methyl-2. -The thermoplastic polyimide precursor solution obtained by polymerization in pyrrolidone was cast and coated by the same method as above and dried at 100 ° C to form a thermoplastic polyimide precursor film. Remove the formed thermoplastic polyimide precursor film from the glass plate at 250 ° C
It is then imidized by heating for 30 minutes, and then a thermoplastic polyimide resin film (5 μm thick, coefficient of linear expansion 5.5 × 10 ⁻⁵ cm
/ Cm / ° C) was prepared.

Then, the copper foil on the above-mentioned one-sided substrate was used in Example 1.
After etching in the same manner as above, replace with nitrogen gas and
Can be heated with a laminating roll with an elementary concentration of 1.5% or less
Laminate a plastic polyimide resin film between each substrate
370 ℃, 50kg / cm ²By heating and pressure bonding under the conditions
A multilayer circuit board (5-layer structure) of the present invention was obtained.

The peeling strength of the multilayer circuit board obtained as described above was 2.4 kg / cm, and the peeling occurred at the interface with the copper foil and not between the polyimide resin layers. Further, no void was generated even in the solder dip test at 400 ° C. for 30 seconds, and there was no problem in heat resistance.

Comparative Example 1 A multilayer circuit board was produced in the same manner as in Example 1 except that the surface of the low linear expansion polyimide resin layer was not treated.

The adhesive force between the two types of polyimide resin layers in the obtained multilayer circuit board was 100 g / cm or less, and a peeling phenomenon was observed at a part of the laminated interface after pressing.

[0044]

EFFECT OF THE INVENTION Since the multilayer circuit board of the present invention is subjected to a specific surface treatment on the surface opposite to the circuit-forming surface of the low linear expansion polyimide resin layer, it is laminated in a multilayer structure through the thermoplastic polyimide resin layer. The interfacial adhesive strength between the respective polyimide resin layers is high and no peeling phenomenon is observed. In addition, since the insulating substrate is substantially formed of polyimide resin, it has the effect of being excellent in heat resistance, chemical resistance, and curl resistance. It can withstand.

Further, by forming a bump-shaped metal protrusion and a through hole having a conduction path in the polyimide resin layer to conduct electricity in the thickness direction of the substrate, the connection with the semiconductor element can be made via the bump, so that the connection can be established. Easy and
Connection reliability and packaging density are improved. Further, since the multilayer circuit board of the present invention can be inspected for good or bad for each board before being multilayered, it is expected to improve the yield in manufacturing.

[Brief description of drawings]

FIG. 1 is a sectional view of each step for explaining a method for obtaining a multilayer circuit board according to the present invention.

FIG. 2 is a cross-sectional view of each step of another manufacturing method for explaining the method for obtaining the multilayer circuit board of the present invention.

FIG. 3 is a sectional view showing another example of the multilayer circuit board of the present invention shown in FIG. 2 (c).

4 is a cross-sectional view showing a state in which semiconductor elements are connected to the multilayer circuit board shown in FIG. 3 via bump electrodes.

FIG. 5 is a cross-sectional view showing a state in which the multilayer circuit board of the present invention on which a semiconductor element is mounted is mounted on an external board.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Copper foil 1'Circuit 2 Low linear expansion polyimide resin layer 2'Low linear expansion polyimide precursor layer 3 Thermoplastic polyimide resin layer 4 Metal 5 Bump-shaped metal protrusion

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Shunichi Hayashi 1-2-1 Shimohozumi, Ibaraki City, Osaka Prefecture Nitto Denko Corporation

Claims (4)

[Claims] 1. A circuit board having a low linear expansion polyimide resin layer on one side of which an etching treatment or a charging treatment is performed and on the other side of which a circuit is laminated is laminated with a thermoplastic polyimide resin layer interposed therebetween. Multi-layer circuit board. 2. A coefficient of linear expansion of a thermoplastic polyimide resin layer
A₁, The total thickness of the thermoplastic polyimide resin layer is t₁,
The linear expansion coefficient of the low linear expansion polyimide resin layer is a ₂, Low line
The total thickness of the expansive polyimide resin layer is t₂If a₁・ [T₁/ (T₁+ T₂)] + A₂・ [T₂/ (T₁+ T₂)] The difference between the value of and the linear expansion coefficient of copper is 1.0 × 10^-Fivecm /
The multilayer circuit board according to claim 1, which is smaller than cm / ° C. 3. At least one through hole is formed in the thickness direction in the low linear expansion polyimide resin layer and the thermoplastic polyimide resin layer in the circuit formation region or in the region and its vicinity and formed in the circuit formation region. The multi-layer circuit board according to claim 1, wherein a conductive path and a bump-shaped metal protrusion made of a metal substance are formed in the through hole, and the circuit boards are electrically connected via the bump-shaped metal protrusion. 4. A step of coating and drying a low linear expansion polyimide precursor solution on a copper foil, a step of subjecting the coated surface to an etching treatment or a charging treatment, and 4 in an inert gas atmosphere.
A step of imidizing the precursor layer by heating at a temperature of 00 ° C. or higher; a step of patterning a copper foil to form a circuit to obtain a circuit board; and a plurality of circuits via a thermoplastic polyimide resin layer. A method of manufacturing a multilayer circuit board, comprising the step of thermocompression bonding the board.